Photothermoelectric (PTE) detection of phase transitions. Application to triglycinesulphate (TGS)

A recently introduced photothermal method, the photothermoelectric (PTE) calorimetry is proposed for the first time in order to detect phase transitions. The capability of both back (BPTE) and front (FPTE) detection configurations in detecting phase transitions is analyzed. It was found that the back detection configuration, with optically opaque sample and thermally thick sample and TE sensor, is very suitable for phase transitions detection; the information, in this configuration, can be collected from both amplitude and phase of the BPTE signal and the amplitude has the possibility of amplifying the critical anomaly of the thermal parameters. In the FPTE configuration, the information about phase transition is contained only in the amplitude of the signal. Using the PTE method, the well-known ferro-paraelectric phase transition of triglycinesulphate (TGS), tacking place at about 49 °C, was investigated. Comparison with the photopyroelectric (PPE) method is performed.